Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnlyHint and idempotentHint annotations, the description discloses additional behavior: 24h cache, provider configurable via environment variable, and that it returns 'encontrado=false' with a diagnostic error instead of throwing exceptions. This adds meaningful transparency about edge cases and operational details.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is structured with clear sections (what it returns, when to use, what it does not do). It is informative without being verbose, and each sentence adds value—no filler or redundant content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers the data returned, the use case, exclusions (sanctions), caching, error handling, and provider configuration. It is contextually rich and provides enough information for an agent to decide when and how to invoke the tool, especially given the output schema exists.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The single parameter 'cnpj' is fully documented in the schema: format (14 digits, with or without punctuation), provider selection (BrasilAPI default, minhareceita via env). The description in the schema covers the parameter completely, and the main description reinforces its purpose.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description explicitly states the tool's function (public CNPJ data from Receita Federal) and enumerates the returned fields (razão social, CNAEs, QSA, etc.). It also differentiates from sibling tools by positioning itself as a complement to compras_perfil_fornecedor_completo and clarifying that it does not cover sanctions, making the purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The 'Quando usar' section provides explicit guidance: use for due diligence, and explicitly directs to sanction tools (CEIS/CNEP/CEPIM/CEAF) when sanctions are needed. It also mentions cache and error behavior, giving clear conditions for its use.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.